Pressure Aging Vessel Test Research Articles

Changing Regularity of SBS in the Aging Process of Polymer Modified Asphalt Binder Based on GPC Analysis

The investigation on aging mechanism of Styrene-Butadiene-Styrene block copolymer (SBS) in polymer modified asphalt binder (PMA) is helpful to the application of PMA and the selection of anti-aging technology. However, it is very complex because of the various chemical molecular structures of SBS and asphalt binder, as well as the complicated physical and chemical reaction between the two components. In order to study the reaction mechanism of SBS in the preparation and service life of PMA, the molecular changes of SBS were studied through gel permeation chromatography (GPC) analysis before and after the rolling thin film oven (RTFO) test and pressure aging vessel (PAV) test of SBS modified asphalt binders. The results showed that the crosslink of SBS was the main reaction in the preparation of PMA with the increasing of molecular weight. The degradation of SBS was a minor reaction in the RTFO aging, and SBS still had enough effect to modify the performance of asphalt binder after RTFO aging. SBS had significant degradation and lost the capability of modifying the performance of asphalt binder because of the decline of molecular weight after PAV aging. The conclusions prove that the GPC method can explain the crosslink and degradation mechanism of SBS. The degradation of linear SBS and radial SBS in PMA is slightly different. The degradation of pure SBS is more serious when it was aged in the PAV test alone (no blending with asphalt binder), compared with the SBS in PMA. The reason is that the SBS in PMA is covered by asphalt binder and has less contact with oxygen.

The Effect of Sodium and Organic Montmorillonites on the Thermal Aging Properties of Bitumen

Effect of sodium and organic montmorillonites on the thermal aging properties of bitumen was investigated by thin-film oven test and pressure-aging vessel test. The microstructures of montmorillonite and the binders were characterized by X-ray diffraction. The results show that the sodium montmorillonite (Na+-Mt) modified bitumen forms a phase-separated structure, while the organic montmorillonite (OMt) modified bitumen forms an intercalated structure. The thermal aging properties of bitumen are improved obviously with the introduction of montmorillonite. Compared with Na+-Mt, the changes of physical properties of bitumen are further decreased by OMt, indicating the good aging resistance of intercalated OMt modified bitumen.

Oxidative aging of asphalt cements from an Ontario pavement trial

This paper documents and discusses a rheological and spectroscopic investigation of the oxidative aging in asphalt cements from a 2003 northern Ontario pavement trial. Seven asphalt cements were aged according to standard methodology (rolling thin film oven test (RTFOT) and pressure aging vessel test (PAV)), as thin films at temperatures of 45, 65, and 85 ℃ and standard pressure (thin film oven test (TFOT)), and under modified PAV conditions (extended time of 40 hours). It was found that the current RTFOT/PAV protocol provided insufficient aging for the poor performing asphalt cements. Infrared analysis of the TFOT-aged samples for the formation of carbonyl groups could largely explain the performance ranking in service. The only significant outlier was modified with polymer and waste engine oil residue. Rheological investigations of the recovered and the TFOT-aged residues were able to show that such materials likely suffer from early gel formation. These findings illustrate the need for improved asphalt cement aging protocols. A preliminary example is provided that shows how simply doubling the PAV aging time to 40 hours can produce materials that more closely replicate those aged for 5-6 years in a northern Ontario climate. It was further confirmed that both chemical and physical hardening tendencies are closely correlated, likely because they involve similar asphalt constituents.

Effect of moisture on the aging behavior of asphalt binder

The moisture aging effect and mechanism of asphalt binder during the in-service life of pavement were investigated by laboratory simulating tests. Pressure aging vessel (PAV) test simulating the long-term aging of binder during the in-service life of pavement was modified to capture the long-term moisture aging effect of binder. Penetration grade tests including penetration test, soften point test, and ductility test as well as Superpave™ performance grade tests including viscosity test, dynamic shear rheometer test, and bending beam rheometer test were conducted to fully evaluate the moisture aging effect of binder. Fourier transform infrared spectroscopy test and Gel-permeation chromatography test were applied to provide a fundamental understanding of the moisture aging mechanism of binder. The results indicate that moisture condition can accelerate the aging of asphalt binder and shorten the service life of asphalt binder. The modified PAV test with moisture condition can well characterize the moisture aging properties of asphalt binder.

The Experimental Research on Durability of Sasobit Modified Asphalt

Sasobit has been applied into asphalt successfully since 1997. From then on, a lot of studies emphasizes on how Sasobit can lower asphalt’s viscosity and reduce poison odor emission. However, the durability of asphalt containing Sasobit is ignored to research. This paper aimed to analyze Sasobit impact on the durability of asphalt. In this study, the Sasobit modified asphalt was blended using different Sasobit contents of 2%, 3%, 4% and 5% by weight of asphalt into the base asphalt (SBS modified asphalt). The Rolling Thin Film Oven test (RTFO) and Pressure Aging Vessel test (PAV) were conducted to simulate the mixing and construction aging and in-service aging of asphalt. The properties and micro-structure of the base asphalt and Sasobit modified asphalt in three different aging states (original state, mixing and construction aging state and in-service aging state) were tested by using the Penetration-Grade system, Performance-Grade system and fluorescence microscope. The aging indexes of the base asphalt and Sasobit modified asphalt were calculated to compare their durability. It was evident that the durability of the Sasobit modified asphalt was mostly affected by the type of base asphalt and Sasobit had a little impaction on the durability of the asphalt.

Rheological and Chemical Properties of Hydrated Lime and Polyphosphoric Acid–Modified Asphalts with Long-Term Aging

The rheological and chemical properties of hydrated lime-polyphosphoric acid (PPA)–modified asphalt binders before and after laboratory oxidative aging were investigated through dynamic shear rheometer (DSR) and nuclear magnetic resonance (NMR) tests. Ten percent by weight of hydrated lime was mixed with 1.5% by weight of PPA-modified asphalt binders. The neat asphalts and multimodified asphalts were subjected to the pressure aging vessel test at a pavement service temperature of 60°C for different durations. The rheological properties of unaged and aged modified asphalts were measured with a DSR at various temperatures. NMR was used to investigate whether hydrated lime reacts with PPA. The rheological results indicate that the addition of hydrated lime to PPA-modified asphalt binders cancels the stiffening effect of PPA. In other words, the addition of PPA to asphalt increases the high-temperature performance grade (PG). The addition of hydrated lime to PPA-modified asphalt removes the benefit of the hig...

Improvement of bitumen performance with epoxy resin

This paper studies the modification of petroleum bitumen with epoxy resin. Different amounts of epoxy were doped into bitumen with 50/70 penetration grade and variations in viscosity as a function of temperature and additive concentration were determined. The effects of the epoxy additive were examined by rheometer, penetration, softening point, DSR (dynamic shear rheometer), DSC (differential scanning calorimeter), RTFOT (rolling thin film oven test), PAV (pressure aging vessel), BBR (bending beam rheometer) and surface tension tests. Adhesion and stability of bitumen aggregate mixtures prepared using original and modified bitumen were compared using Nicholson stripping and Marshall tests. The optimum dosage of the additive yielding the best rheological and performance properties was found to be 2% (w/w). Appreciable decrease in the formation of rutting, bleeding, stripping and cracking of modified bitumen may be obtained through epoxy addition.

Influence of accelerated aging test temperature on the properties of binders

This study investigated the influence of test temperature of the rolling thin film oven (RTFO) and pressure aging vessel (PAV) on aging of asphalt binders. It also evaluated the difference of three binders obtained at 85 and 100°C, as recommended by European and SHRP binder specifications for PAV, and at a typical pavement temperature of 60°C. The aging was evaluated in terms of the physical, chemical and rheological properties. Tests conducted included penetration, softening point, viscosity, mass loss, chemical compound analysis, infrared absorption spectrum (IR), gel permeation chromatography (GPC), bending beam rheometer (BBR) as well as dynamic shear rheometer (DSR). The results indicated that: (1) the hardness of the aged binders was sensitive to the RTFO test temperature, whereas, their Performance Grade (PG) was not affected; (2) increasing the PAV test temperature enhanced the oxidation aging, leading to significant changes in the properties; (3) the three aged binders obtained at PAV temperatures of 60, 85 and 100°C have insignificant difference in terms of the considered properties.

Surfactants in Aged Asphalt and Impact μ on Moisture Susceptibility of Laboratory-prepared Mixes

ABSTRACT Short-term aging (rolling thin-film oven test) of an asphalt binder resulted in the production of surfactants (surface-active compounds), while long-term aging (pressure aging vessel test) of asphalt binders resulted in the production of not only surfactants but also strong acids. The strong acids were identified as being sulfonic acids. It was proposed that the generation of surfactants and/or sulfonic acids in asphalt binder would promote moisture damage in asphalt-aggregate mixes. The surfactants could act as a detergent and emulsify components of the mix, and sulfonic acids could attack the aggregate surface, thus, disrupting the asphalt-aggregate interface. A model compound, p-dodecylbenzenesulfonic acid, which incorporates these two structural features, was used as a modifier in several different mixes. Briquets fabricated from the modified mixes were tested for moisture susceptibility using the freeze-thaw pedestal test. It was observed that those mixes, which were originally not susceptible to moisture damage, were now susceptible. It was also noted that the addition of lime to the aggregates prior to the fabrication of the briquets counteracted the influence of p-dodecylbenzenesulfonic acid.

Quantitative Effect of Elastomeric Modification on Binder Performance at Intermediate and High Temperatures

An experimental study was conducted to characterize the dynamic mechanical properties of elastomer-modified asphalt binders at intermediate and high temperatures. Two types of elastomeric modifiers, styrene-butadiene-styrene ~SBS! and styrene-ethylene/ butylene-styrene ~SEBS!, were used at three different concentrations. Short-term aging and long-term aging were simulated by the rolling thin film oven test and the pressure aging vessel test, respectively. A dynamic shear rheometer was used to conduct frequency sweeps at temperatures ranging from 5°C to 75°C in increments of 10°C. Two fitting models were introduced to describe the variation of the selected parameters with temperature. An investigation of the resulting isochronal plots indicated that polymer modification is effective in increasing rutting resistance at high temperatures and fatigue resistance at intermediate temperatures. It was also found that SBES improves the binder rutting resistance more than SBS. However, SBS was found more effective in improving the binder fatigue resistance at intermediate temperatures.

Study of Strategic Highway Research Program Pressure Aging Vessel Procedure Using Long-Term, Low-Temperature Aging Experiments and Asphalt Kinetics

An essential element of understanding and predicting long-term asphalt binder performance is understanding asphalt oxidative aging and its effect on physical properties. High-temperature, high-pressure laboratory kinetic studies, pressure aging vessel (PAV) aging, and aging at pavement conditions are compared. The consequences of running the PAV at conditions far from road conditions are examined. An aging model previously reported in the literature was used to describe the data. Important asphalt aging parameters include the pressure reaction order (α), activation energy ( E), initial jump in carbonyl content, and hardening susceptibility. All of these parameters are asphalt dependent. PAV tests were performed on asphalts for which kinetic data were available, and the results were compared with the kinetic model and with results obtained after 135 days of aging at 333 K (140°F) air. The high temperature and pressure used in the PAV test sometimes results in serious errors in the performance ranking of asphalts of different E and α. Nevertheless, the test often ranks asphalts remarkably well because of fortuitous cancellation of several effects of pressure and temperature and the dampening effects of diffusion. Diffusion slows the oxidation rates, and asphalts with higher rates harden at the surface faster, increasing the diffusion resistance and slowing the observed bulk rate. The relative hardening of different asphalts is affected by the choice of PAV time, temperature, and pressure.